The NREL process, illustrated in Fact Sheet 1, consists of a plurality of fluid beds wherein the first fluid bed is a gasifier through which hot olivine (sand) is recycled that indirectly heats the biomass to cause it to release its volatile matter in the form of a tar-containing raw syngas. The fluidization of the biomass in the gasifier is effected by means of steam, with the sand being heated in a first combustion chamber which is separate from the gasifier, using char as a fuel. Downstream of the gasifier, a second fluid bed is provided as a tar reformer through which a hot, regenerated, nickel-based catalyst is circulated which heats the tar-containing raw syngas in order to crack its tar into lighter hydrocarbons. The fluidization medium in the second fluid bed, in which the raw syngas is converted to a tar-free syngas, is also steam, with its catalyst being recycled and heated in a second combustion chamber that is separate from the tar reformer, using a diverted side stream of raw syngas, which is characterized as a “diverted syngas,” from the main stream of the raw syngas that is being fed from the gasifier to the tar reformer. This side stream serves as the fuel in the second combustion chamber, within which the tar containing raw syngas is converted to a “tar-free syngas.” At this stage, the tar-free syngas is cooled and scrubbed into a “dry syngas” in a separate chamber that serves as a “Quench and Scrubber.”
Since the process of NREL described herein operates at low pressure (23 psi), and to produce methanol requires a pressure of about 750 psi, the dry syngas is compressed and directed to a water-gas shift in order to increase the ratio of H2 to CO, and in so doing, CO2 is formed. Up to this point, no sulfur provision is made to remove the sulfur in the form of H2S from the syngas stream; this results in a mixture of gases whose composition includes syngas, CO2, and H2S that is fed to a separator from which three separate gases are produced—namely, CO2, which is discharged to the atmosphere; H2S directed to a sulfur plant where it is treated at low temperature with amine; and a clean syngas directed to a methanol plant to produce methanol that is converted to gasoline by the known MTG process that belongs to ExxonMobil.
It is to be noted that the instant invention of the Applicant does use the same technology relating to the making of methanol which is converted to gasoline (MTG) of ExxonMobil as NREL, but the complexities and disadvantages of the NREL process that produces the syngas to make the methanol are evident, especially when compared to the Applicant's invention, as listed in Fact Sheets 2 and 3, which deals with the conversion of the biomass into the clean syngas that serves as the feedstock (resource) to produce the methanol that would be converted to gasoline or to any other biofuel or chemical.
In particular, the main outstanding disadvantage of the NREL process is the massive solids recycling that takes place in the circulation of the olivine (sand) to indirectly heat the biomass in the gasifier that requires for every one (1) pound of biomass, twenty-seven (27) pounds of hot olivine need to be circulated (reported by NREL on page 18, paragraph 5, of its Final Report, which was made public in January 2011. Since the capacity of the facility was designed to feed 2,205 tons per day of biomass, it means that 59,535 tons per day of olivine would have to be circulated from the char combustion chamber to the gasifier and from the gasifier back to the char combustion chamber. This amount of solid movement is impractical, especially for the puny daily production of only 2,857 barrels of oil equivalent.
Other NREL disadvantages are as follows:                An unrealistic capacity factor of 96% in view of the potential abrasive properties of hot sand circulating to and from gasification equipment through pipes will require frequent maintenance and quite possibly frequent replacement which will cause complete shut downs of the NREL process;        Low process pressure in gasification, tar reforming, and quenching, gas scrubbing; and catalyst indirect heating;        Indirect heating of biomass by the olivine;        Excessive use of water and its treatment;        Water-gas shift, producing CO2;        Char combustion, producing flue gas containing CO2;        No provision for CO2 conversion to useful product;        Inefficiency in syngas compression;        Heat losses from massive solids recycling;        Cold syngas cleanup;        Wet quenching and scrubbing;        Amine sulfur removal;        Ash production, which is expensive to dispose;        The use of expensive catalyst;        High capital cost; and        No provision for guaranteeing availability of biomass resource to provide sustainability.        